1. Field of the Invention
This invention relates generally to an electronically controlled sample warper having one or more yarn introduction levers to warp yarns on a warper drum in the preset order with automatic yarn change, and more particularly to such an apparatus which enables efficient exchange of yarns to be wound on the warper drum.
2. Description of the Related Art
Conventional electronically controlled sample warpers are disclosed, for example, in Japanese Patent Publication No. SHO 64-8736. The disclosed sample warper includes driving and driven shafts projecting centrally from opposite ends of a hollow shaft. A first small gear fixed to a pulley is loosely mounted on the driving shaft, while a second small gear fixed to a yarn introduction lever is loosely mounted on the driven shaft. The first and second small gears are cooperative with each other via meshing engagement with third and fourth small gears, respectively, mounted on opposite ends of a cooperation shaft extending through the hollow shaft. The hollow shaft is cantilevered at the driving-shaft side. Drum frames are mounted on the driven-shaft side of the hollow shaft and each have an outer periphery having alternately an arcuate portion and a straight portion. A pair of rollers is disposed one on the arcuate portion of each of the drum frames. A warper drum is loosely mounted on the hollow shaft and has horizontal drum spokes carrying the rollers around which conveyor belts are wound. The conveyor belts are simultaneously driven to a common amount of fine movement by a drive member threadedly engaged with interior screw shafts of planetary gears meshing with a sun gear suitably driven from the exterior. As the sun gear rotates, the planetary gears rotate concurrently. The yarn introduction lever has a distal end bent inwardly to provide a yarn introducing part disposed adjacent to the front end of the outer periphery of the warper drum. The warper also includes: a shedding means for forming a shed and a cut shed by selecting warp yarns (to be wound on the warper drum) over and under shedding bars and cut shedding bars; a total yarns counter count means for rendering an up signal, of a total counter for counting the total number of the warp yarns, to be on or off; a total yarns completion termination means for terminating the operation of the warper when the total number of the warp yarns reaches a predetermined value; a conveyor belt leftward moving means for moving the conveyor belt leftwardly; a conveyor belt rightward moving means for moving the conveyor belt rightwardly; an operation/termination means for transmitting the rotation of a main motor to the yarn introduction lever; a yarn selection means for controlling a yarn selection guide and a yarn removing unit; a yarn pressing solenoid means for rendering a solenoid of a yarn slack preventing (yarn pressing) unit operative and inoperative; and a windings count means for counting the number of windings of the yarns so as to display the counted result. By selecting the kind of yarn 0-n, and setting the number of yarn, the number of repeats, the number of windings, the quantity of movement or feed of the conveyor belt, a desired pattern of warping can be achieved automatically.
The electrically controlled sample warper described above has been developed by the present assignee and has acquired a good reputation for its capability of automatic pattern warping.
However, in this conventional sample warper, since the main motor is comprised of an ordinary motor, it is impossible to vary the rate of rotations during operating so that miscatches and mischanges as well as yarn breakage are inevitable when exchanging yarns. Furthermore, it is impossible to perform cushion start and stop, and jogging operation, thus posing a room for improvement in the operation efficiency.
For setting the density of warp yarns, the rate of moving the conveyor belt is determined by varying the gear ratio of speed change gears operatively connected to the main motor. Since the conveyor belt is moved even during idling, regular windings of yarn on the warper drum are difficult to achieve so that the tension and the warping length would finally vary during the winding operation.
In order to overcome the above-mentioned problems, proposals have been made by the present assignee to employ an inverter motor and an AC servo motor in the sample warper (Japanese Patent Publications Nos. SHO 64-10609 and SHO 64-10610).
In a sample warper provided in accordance with another prior proposal, a plurality of warp yarns can be concurrently wound on a warper drum with omitting a yarn exchanging step to eliminate any time loss for the yarn exchange, thus reducing the warping time (Japanese Patent Publication No. HEI 4-57776).
According to a further improvement proposed by the present assignee, warping on a sample warper is performed such that after a first winding of yarn is formed on a warper drum, the yarn for the next winding is placed ahead of an end of the first or preceding winding of yarn. Thus, the sample warper is able to warp yarns on the warper drum, with windings of the yarns neatly layered one above another in regular order, thereby enabling the yarns to be readily rewound on beans on a weaving machine even when the warping length is relatively large (Japanese Patent Laid-open Publication No. HEI 7-133538).
The improved sample warpers have already acquired a very good reputation.
The proposed electronically controlled sample warpers have a yarn exchange mechanism illustrated in FIG. 24 of the accompanying drawings. As shown in this figure, a yarn selection guide unit 27 has a plurality of yarn selection guides 27a-27j for selecting and guiding a yarn 22. The yarn selection guides 27a-27j each have one rotary solenoid 29 associated therewith. When the rotary solenoid 29 is turned on, the corresponding yarn selection guide 27a-27j is angularly moved or turned in one direction to advance to an operating position (yarn exchange position). Conversely, when the rotary solenoid 29 is turned off, the yarn selection guide 27a-27j is turned in the opposite direction to return to a standby position. In the conventional yarn exchange mechanism, a yarn introduction lever 6 is used to wind the yarn 22 on a warper drum A while exchanging the yarn 22. The yarn 22 supplied from a creel passes between a yarn introduction cover 59 and a stop plate S, then is held by the yarn introduction lever 6, and subsequently wound on the warper drum A. The yarn selection guides 27a-27j have a shape or configuration which, as shown in FIG. 25, is formed by a straight arm (27e being shown) bent at its distal end portion in the same direction as the direction of rotation of the yarn introduction lever 6.
In the conventional sample warper, when the yarn 22a on the yarn selection guide 27a is to be changed to a yarn 22e on the yarn selection guide 27e, for example, a yarn removing unit 32 mounted on a base Y is activated so that after the yarn introduction lever 6 has passed the yarn selection guide device 27, the yarn 22a is removed by a yarn remover 32a from the yarn introduction lever 6 (FIG. 26). A guide rod 59a projecting from the inner surface of a lower portion of the yarn introduction cover 59 guides the removed yarn 22 between the base Y and the stop plate S where the removed yarn 22 abuts on one yarn selection guide 27a which has already been advanced to the yarn exchange position and urged against the stop plate S (FIG. 27).
Then the yarn selection guide 27a is turned toward the base Y to retract into the standby position during which time the removed yarn 22a is held or caught by the yarn selection guide 27a and received in the base Y (FIG. 28).
Thereafter, the yarn selection guide 27e holding thereon a yarn 22e to be next wound on the warper drum A is turned from the base Y toward the stop plate S to reach the yarn exchange position (FIG. 29). Then, the yarn introduction lever 6 passes the position of the yarn selection guide 27e in which instance the yarn 22e is caught by the yarn introduction lever 6. The yarn 22e while being caught by the yarn introduction lever 6 is then wound on the warper drum A (FIG. 30). The yarn selection guide 27e is turned to return to its standby position and held in the standby position while the yarn 22e is continuously wound on the warper drum A (FIG. 31). By the foregoing sequence of operations, the yarn exchange is performed.
In the conventional yarn exchange mechanism, however, the yarn remover 32e is inserted between the yarn introduction lever 6 and the stop plate S so as to keep the yarn 22 immovable in the direction of rotation between the creel and the yarn remover 32a until the yarn 22 is removed from the yarn introduction lever 6.
The yarn 22 which is prevented by the yarn remover 32a from moving in the rotating direction is detached from the yarn introduction lever 6 while sliding on the same.
In this instance, the yarn 22 needs to be continuously supplied from the creel during a time from its abutment on the yarn remover 32a to its detachment from the yarn introduction lever 6. Since the yarn during the yarn changing passes along a different path from the yarn while being wound on the warper drum A, the length of the yarn required for the yarn changing is further elongated. In addition, due to the use of the yarn remover 32a, the yarn is subjected to an impact force or shock when it is removed or released from the yarn introduction lever 6.
For the reasons described above, the removed yarn tends to slack or is affected by static electricity before it is received or store in the base Y, failing to be received adequately in the base Y.
This problem becomes serious when the yarn exchange is performed at high speeds. Accordingly, high speed yarn change is difficult to achieve. In addition, since the yarn remover 32a is attached to the base Y, only one position is available for the attachment of the yarn remover 32. Accordingly, those yarn which are located remotely from the yarn remover 32a cannot be exchanged without difficulties, resulting a limited total number of yarns that can be used on the sample warper.